Flight control systems (sometimes referred to as “flight controllers”) translate inputs received from manually operated pilot controls, such as one or more of a roll stick, rudder pedals, pitch stick, collective, and throttle controls, etc., referred to collectively herein as “inceptors”, and/or inputs from one or more sensors (e.g., air speed) into commands to the flight control assets of the aircraft, which may include one or more of control surfaces, such as rudders, ailerons, elevators, etc.; sources of forward thrust, such as propellers or jet engines; powered sources of lift such as rotors or lift fans; and forces capable of being directed or otherwise controlled or concentrated through use of nozzles, diverters, physical structures onto which engine or fan thrust may be directed, such as vanes, etc. and/or rotation of thrust generating devices.
Each of the foregoing, and/or other equipment and structures, may be used to affect one or more of the speed, direction, and attitude/orientation of the aircraft, and depending on the input each may be able to contribute to satisfying a command/input received via one or more inceptors. Aerodynamic control surfaces, powered sources of control forces, such as lift fans, and other structures capable of affecting aircraft attitude, motion, and/or orientation are referred to collectively herein as “actuators”.
An aircraft typically is considered to have six degrees of freedom of movement, including forces in the forward/back, side/side, and up/down directions (corresponding to forces in three axes Fx, Fy, and Fz) and moments about the longitudinal (roll) axis, the transverse (pitch) axis, and the vertical (yaw) axis (corresponding to moments in three axes Mx, My, and Mz). If an aircraft has more actuators than degrees of freedom, it must be determined how the various actuators will be used to act on the aircraft in response to commands received via the inceptors or sensors. For a given set of one or more pilot commands under given circumstances, some combinations of actuators capable of acting on the aircraft to achieve the result indicated by the pilot command(s) may be more effective and/or efficient than others. For example, some may consume more or less power and/or fuel than others, provide a more smooth transition from a current state than others, etc. Considered circumstances may include the current position of the aircraft. In the event of an aircraft with dynamic geometry, the position of an aircraft component (e.g. a tiltwing) may be considered in determining the actuator commands. Constraints such as evenly distributed thrusts or actuator limitations may be considered in determining the actuator commands. Even for systems that are not over-actuated, it is necessary to determine what combination of actuation commands results in the desired motion and how to manage saturation issues or enforce system constraints.
In prior systems, attempts have been made to pre-compute, offline, combinations of actuators and associated parameters (e.g., position, speed, other parameters) to respond to different combinations of inceptor input using heuristics and/or engineering judgement. However, typically it is not possible to determine in advance every combination of actuators and associated parameters that may be required under all possible conditions and circumstances.